//when I try this for a language selection button

function clickEnglish(event:MouseEvent) {
trace("you clicked english");
var loadit = new Loader();
addChild(loadit);
loadit.load(new URLRequest("index_nu_horizontal.swf"));
}

englishButton.addEventListener(MouseEvent.CLICK,clickEnglish);

//gives this error
TypeError: Error #1009: Cannot access a property or method of a null object reference.
	at thumbClass()
	at thumb_bar_Mc()
	at flash.display::Sprite/constructChildren()
	at flash.display::Sprite()
	at flash.display::MovieClip()
	at mainClass()